This study investigated the effects of ingesting caffeine or a placebo on resistance exercise performance, mood, heart rate, and rating of perceived exertion over an entire resistance exercise bout in resistance-trained males (N = 9). During each trial, Ss performed four major multi-joint resistance exercises (2 sets of 10 repetitions followed by 1 set to exhaustion) with two minutes rest between sets. Investigators measured ratings of perceived exertion, heart rates, and Profile of Mood States before, during, and after each trial.

There were no significant differences between conditions in total repetitions or rating of perceived exertion during the final set of each exercise. Heart rate during caffeine trials significantly exceeded placebo at several time points during the first two exercises. Significant main effects indicated that the POMS factors of Tension-Anxiety, Depression-Dejection, Anger-Hostility, and Total Mood Disturbance in the caffeine condition significantly exceeded the placebo condition.